Work machines such as, for example, dozers, loaders, excavators, motor graders, and other types of heavy machinery use linkage systems to accomplish a variety of tasks. These linkage systems often include hydraulic cylinders. Problems can be encountered in the operation of a hydraulic cylinder if a piston within the hydraulic cylinder impacts against an end structure of the hydraulic cylinder. Such impacts can disturb work operations, cause undesirable noise, and can cause damage to the cylinder or other components of the linkage system. To prevent such problems, a variety of sensors and electro-hydraulic devices are used to cushion the end of a piston stroke within the cylinder. These cushioning devices can include cylinder position sensors that are in communication with electronically actuated hydraulic valves.
For example, U.S. Pat. No. 6,509,733 (the '733 patent) issued to Blugaugh et al. on Jan. 21, 2003, describes a fluid cylinder having an embedded positioning sensor. The fluid cylinder includes a cylinder body having an internal cavity, a piston and rod assembly disposed within the internal cavity, and end caps enclosing the internal cavity. A sensor is disposed within an end cap for sensing a distance of the piston or rod from a predetermined location and outputting signals representative of the distance. This distance information may then be used to manipulate electronically actuated hydraulic valves that control both the position and speed of the fluid cylinder.
Although the fluid cylinder system of the '733 patent may provide position and velocity information for controlling electronically actuated hydraulic valves to prevent piston-to-cylinder impact, the fluid cylinder system may be unable to provide piston-to-cylinder impact protection in the case of a malfunction of components of the system that includes the electronically actuated hydraulic valves. In addition, the positioning sensor of the '733 patent may not assist in avoiding piston-to-cylinder impact in hydraulic systems that do not utilize electronically actuated hydraulic valves.
The disclosed hydraulic cylinder is directed to overcoming one or more of the problems set forth above.